Research Objectives: This renewal grant request is to provide continued support for research exploring the relationships of sodium transport, renal tubular permeability and metabolism in the mammalian renal nephron. Effects of cyanide, iodoacetamide and 2, 4 dinitrophenol on renal cortical and medullary adenine nucleotide content will be correlated with their effects on renal oxygen consumption and tubular function. Studies to determine the effects of renal arterial, and renal venous clamping and of elevated ureteral pressure on individual nephron function and renal oxygen consumption will be performed and compared to our previous results in hydropenic and volume expanded rats. Techniques to measure pyruvate, lactate, and glucose in tubular fluid and peritubular capillary plasma will be established to study the glycolytic capacity of the proximal tubule in vivo. These studies will be extended as indicated by the results to explore the specific nature of in vivo tubular aerobic metabolism.